Systems, devices and methods for thermal testing of an optoelectronic module

ABSTRACT

Devices, systems and methods for thermal testing of optoelectronic modules are disclosed. The device includes a frame member, a thermoelectric cooler, a plate in thermal contact with the DUT, a heat sink in thermal contact with the frame, and a metallic clip for attaching the thermal testing device to the module (DUT). The clip secures the thermoelectric cooler to the DUT. The method includes the steps of providing a testing apparatus having a printed circuit board with a test circuit formed thereon. The test board also has an electrical interface disposed in electrical communication with the test circuit, and a thermal testing assembly. A temporary electrical connection is formed between the DUT device and the interface. The thermal testing assembly is used to maintain a test temperature of the DUT device. A data stream is transmitted through the DUT device and then evaluated for adherence to a defined specification.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional, and claims the benefit, of U.S. patentapplication Ser. No. 11/027,765, entitled SYSTEMS, DEVICES AND METHODSFOR THERMAL TESTING OF AN OPTOELECTRONIC MODULE filed Dec. 30, 2004, nowU.S. Pat. No. 7,260,303 which, in turn, claims the benefit U.S.Provisional Patent Application No. 60/534,046, filed Jan. 2, 2004. Allof the foregoing patent applications are incorporated herein in theirrespective entireties by this reference.

BACKGROUND

1. The Field of the Invention

The present invention relates generally to the field of optoelectronicdevices, and more particularly, to systems, devices and methods fortemperature cycle testing of optoelectronic transceiver modules.

2. Related Technology

Optoelectronic transceiver modules are commonly employed in fiber opticdata transmission networks in the transmission and receipt of binarydata signals. Among other things, an optoelectronic transceiver includesan optical transmitter, such as a laser, that receives electrical datasignals, translates the electrical data signals to optical data signals,and then transmits the optical data signals. Further, the optoelectronictransceiver also includes an optical receiver, such as a photodiode,that receives optical data signals, translates the optical data signalsto electrical data signals, and then transmits the electrical datasignals. Optoelectronic transceivers can also include a printed circuitboard (PCB) containing various control circuitry for the opticaltransmitter and/or optical receiver.

When manufacturing optoelectronic transceiver modules, each transceiveris tested to ensure that it functions properly. Since optoelectronictransceivers operate in environments characterized by any number ofvarying conditions, such as temperature and supply voltage for example,the transceivers are typically tested under conditions similar to thoselikely to be experienced in the intended operating environment.

However, for a number of reasons, testing optoelectronic transceivermodules has proven to be a costly activity. One reason for this is thatoptoelectronic transceivers are not readily disassembled or repairedonce their components have been assembled. In this regard, it isgenerally the case that an optoelectronic transceiver will malfunctionif there is a defect in the electrical component, such as the PCB,either of the optical components, or the connections between components.Thus, correction of the problem or defect often requires disassembly ofthe transceiver which, as noted above, can be difficult and,accordingly, rather costly.

Additionally, one of the aspects of the optoelectronic module that canbe tested is the ability of the module to function over a widetemperature range. Typically, this has been accomplished by attachingthe module to a testing board and placing the entire test board andmodule combination into an oven for testing over a range oftemperatures. This approach to testing has proved problematic. Forexample, the printed circuit boards used as the testing boards are notdesigned to operate in the same temperature range as the optoelectronicmodules. Therefore, when these boards are heated, they frequently fail,resulting in increased time and expense to conduct the tests on themodules, as well as time and expense to repair any damage to the testboards. Also, precise control of the module temperature is difficult toachieve in the oven due to variables such as the presence of aircurrents within the oven.

One approach to such problems has been to test the optoelectronic modulecomponents individually, and then assemble the module. While such anapproach may help to eliminate the problem of determining whichparticular component is malfunctioning when the module is tested as awhole, such an approach may not provide useful information concerningthe performance of the assembled module. Rather, the module must stillbe tested after final assembly to ensure that all connections areworking properly. Thus, typical testing evolutions have involved a timeconsuming, and expensive, two step testing process where the module wastested firstly in the oven at one temperature and then secondly in theoven at a second temperature.

BRIEF SUMMARY OF THE EMBODIMENTS

In view of the foregoing, and other problems in the art, what is neededare systems, methods and devices for testing optoelectronic modules thateliminate, or at least attenuate, the problems discussed above. Amongother things, such systems, methods and devices should enablemodule-specific thermal testing over a desired temperature range. Thesystems should allow the operating environment of the modules to beeasily changed to make the testing process fast and efficient. Suchsystems, devices and methods are disclosed herein.

One exemplary embodiment of the present invention provides a thermaltesting assembly that is suitable for thermal testing and cycling ofcomponents, such as optoelectronic modules. Exemplarily, the thermaltesting assembly can include a cover, a thermoelectric cooler (“TEC”)attached to the cover, a cover plate that comes into contact with themodule, and a metallic clip attached to the cover plate. The metallicclip can be configured to enable removable attachment of the thermaltesting assembly to a cage within which the device under test (DUT) isdisposed. The TEC is thus arranged for substantial thermal contact withthe cage and the DUT. Additionally, a temperature sensor can be providedand attached indirectly to the DUT to enable collection of feedback dataconcerning the temperature of the module. Finally, a heat sink can beprovided on top of the frame to help maintain the temperaturedifferential needed by the TEC.

In the operation of the thermal testing assembly, a temporary electricalconnection can be formed between the optoelectronic device under test,and an electrical interface included in the board upon which the cageresides. Following connection, power is applied to the TEC to bring theDUT to a desired temperature. The thermal testing assembly thenmaintains the test temperature of the DUT at a desired temperature, orwithin a desired temperature range. In some exemplary embodiments, thistemperature range can be about −40 degrees C. (° C.) to about 100° C.Once the DUT reaches the desired temperature, a data stream istransmitted through the optoelectronic device and evaluated forconformance with a defined specification. The specification can include,by way of example and not limitation, those operating parametersspecified by the current XFP Multi-Source Agreement (MSA) Specification,SONET OC-192 SR-1 and SDH STM I-64.1 specifications, as well as the10-Gigabit Ethernet, IEEE 802.3ae, 10 GBASE-LR/LW, and 10 G FibreChannel specifications.

In this way, the thermal testing assembly enables full data rate testingof the DUT over a defined operating temperature range, at data ratesranging from, for example, about 1 Gb/s to about 11 Gb/s. This helps toensure that transceivers that are shipped to customers will perform asspecified, thus greatly reducing module failures and increasing customersatisfaction. Moreover, the need to thermally cycle the entire testingboard with which the optoelectronic device is associated issubstantially eliminated.

One exemplary method for testing an electronic, optical, oroptoelectronic device can include a first optional step for preheatingthe device to a desired testing temperature. Once preheated, the devicecan be placed in a thermal testing assembly and electrical and/oroptical connections to a testing device are made. The thermal testingassembly can be identical to or similar to the testing assemblydescribed above. The next step is to bring the device to a desiredtesting temperature, or, if preheated, maintaining the device at thattemperature. A data stream can then be transmitted from the testingassembly through the device under test. Finally, the data stream can beevaluated according to one or more predefined standards, such as thosediscussed above.

These and other objects and features of the present invention willbecome more fully apparent from the following description and appendedclaims, or may be learned by the practice of the invention as set forthhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other aspects of embodiments of thepresent invention, a more particular description of the invention willbe rendered by reference to specific embodiments thereof which areillustrated in the appended drawings. These drawings depict onlyexemplary embodiments of the invention and are, therefore, not to beconsidered limiting of the scope of the invention. The invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIG. 1 shows a perspective schematic view of an exemplary optoelectronictransceiver module such as may be evaluated with a thermal testingassembly;

FIG. 2A is an exploded perspective view illustrating aspects of anexemplary implementation of a thermal testing assembly;

FIG. 2B is an exploded perspective view illustrating aspects of analternate exemplary implementation of a thermal testing assembly;

FIG. 3 is a block diagram illustrating aspects of an exemplaryoptoelectronic transceiver module test system;

FIG. 4 is a block diagram of the exemplary optoelectronic transceivermodule test system of FIG. 3 showing a module in a testing position;

FIG. 5 is a block diagram of another exemplary embodiment of anoptoelectronic transceiver module test system showing a module in atesting position; and

FIG. 6 is a flowchart illustrating aspects of an exemplary method forthermal testing of an optical component of an optoelectronictransceiver.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present invention relate to devices, systems andmethods used in the thermal testing of optical, electronic, oroptoelectronic devices, such as, but not limited to, optoelectronictransceiver modules. Embodiments of the invention enable module-specificthermal testing by way of a portable thermal testing assembly. Thethermal testing assembly can be incorporated into an exemplary testingsystem. The resulting system and corresponding method allow modules tobe tested over a wide temperature range. Additionally, some embodimentsof the testing assembly systems and methods allow many modules to betested in a shorter amount of time than prior systems and methods.

A typical module, such as can be tested using embodiments of the presentinvention, is shown in FIG. 1 and designated generally as referencenumeral 100. Module 100 is exemplarily implemented as an optoelectronicmodule. It should be noted however, that embodiments of the inventionare not constrained solely for use in testing optoelectronic modules.Rather, exemplary embodiments of the invention may be used in anytesting evolution or test setup where the functionality disclosed hereinmay prove useful. For example, electronic modules, optical modules, andother types of electronic or optoelectronic devices can be tested usingthe devices and methods disclosed herein. Accordingly, the scope of theinvention should not be construed to be limited to the exemplary testevolutions and test setups, nor to the exemplary devices under test,that are discussed herein.

With continuing reference to FIG. 1, the module 100 has a housing 102which exemplarily includes a one piece metal housing, but othermaterials and methods of construction can also be employed. In alternateexemplary embodiments, housings having more than one piece, and/or thatare constructed from nonmetallic materials, can also be used. In oneexemplary embodiment, the module 100 can be a 10 Gigabit per second(Gb/s) small form-factor pluggable (XFP) module. However, as notedearlier, exemplary embodiments of the invention may be usefully employedwith a wide variety of other components as well, such as, but notlimited to, SFF, SFX, SFP, GBIC, and AT modules.

Disposed within the housing 102 are various optoelectronic componentsadapted to implement the functionality associated with the module 100.Exemplarily, a first optical sub-assembly (OSA) 104 and a second OSA 106are located side by side near a front end 108 of the housing 102. Ofcourse, the OSAs may be arranged in other ways as well. Moreover, feweror more OSAs may be employed in exemplary optoelectronic modules.

In the exemplary illustrated implementation, one OSA can be a “receive”OSA (ROSA), while the other OSA can be a “transmit” OSA (TOSA), althoughboth OSAs 104, 106 may be of the same type in some applications. Ingeneral, the ROSA receives an input optical data signal and converts theinput optical data signal into an output electrical data signal.Conversely, the TOSA receives an input electrical data signal andconverts the input electrical data signal into an output optical datasignal. In other exemplary embodiments, multiple TOSAs and/or ROSAs canbe employed in a single module.

Also located within the housing 102 can be a printed circuit board (PCB)(not shown). In one exemplary embodiment of the module 100, the PCBincludes electrical connectors 112 (shown in phantom), located proximatea rear end 110 of the housing 102, which are configured and arranged toelectrically and mechanically connect the module 100 to another device.The electrical connectors 112 can be any type of electrical connectorthat facilitates an electrical connection between the module 100 and thetesting apparatus and/or other components with which the module 100interfaces. Additionally, the electrical connectors 112 can be either amale, a female, or a universal (neither male or female) type connector.

In some instances, the OSAs 102 and 104, as well as the PCB, areindividually tested and confirmed to be operating properly before finalassembly and testing of the module 100. However, this need not be thecase. Embodiments of the invention can be used to test any assembledmodule, as well as modules in various stages of assembly or completion.Alternately, other types of electrical or optical components thatrequire testing over a temperature range can also be accommodated withinthe exemplary embodiments.

FIG. 2A illustrates various aspects of a thermal testing assembly 200according to one embodiment of the present invention. Thermal testingassembly 200 includes a cover 202 that, among other things, isolates theassembly from the ambient air temperature. The thermal testing assembly200 further includes a thermoelectric cooler (TEC) 204 that is locatedsubstantially within, and which is in thermal contact with the cover202. Alternately, the TEC 204 can be attached to the cover 202.Immediately below, and attached to the TEC 204, can be a clip 210designed to hold the thermal assembly 200 onto the cage housing thedevice under test (DUT). The thermal testing assembly 200 furtherincludes a cover plate 212 that is secured against the optoelectronicdevice under test using the clip 210 and is simultaneously held inthermal contact with the TEC 204.

The cover 202 is substantially comprised of a thermally conductivematerial, such as metal, to enable heat transfer. Examples of suchmetals can include, but are not limited to, aluminum, aluminum alloys,copper, and/or copper alloys. The cover 202 exemplarily includes shieldportions 202A that serve to at least partially isolate the TEC 204 fromair currents or other influences that may compromise the performance ofthe thermal testing assembly 200. The geometry, positioning andorientation of the shield portions 202A are exemplary only. The shieldportions 202A may, more generally, be implemented, arranged, and/ororiented in any fashion that a particular situation or application mayrequire.

As noted earlier herein, the thermal testing assembly 200 includes theTEC 204 located substantially within, and attached to the cover 202.Electrical supply wires 206 and 208 can connect to the TEC 204 forconnection with an electrical power source (not shown) for operation ofthe TEC 204. The TEC 204 serves to establish and maintain the DUT at adesired temperature. Examples of such DUTs can include, by way ofexample and not limitation, the module 100 (see FIG. 1), or any otherelectronic, optical or other configurations of optoelectrical orelectrical devices. In some implementations, the TEC 204 is alsoemployed to change the temperature of a given DUT. Depending on themanner in which current is supplied to the TEC 204, the TEC 204 may beemployed to either heat or cool the DUT, or to maintain the DUT at adesired operational temperature, as discussed in more detail below.

The clip 210 enables the thermal testing assembly 200 to be removablyattached to, for example, a cage assembly that holds the DUT. Forinstance, the clip 210 can include grooves 222 on arm portions 224 thatreceive and releasably hold a cage housing the DUT. Examples of suchDUTs can include the module 100 (see FIG. 1), or any other electronic,optical or other device upon which thermal testing is to be conducted.Module 100 can be, by way of example and not limitation, an XFP module,an SFF module, an SFP module, an SFX module, an AT module, a GBIC moduleand/or other modules known to those of skill in the art.

The clip 210 is one structural implementation of a means for removablyattaching the thermal testing assembly to a device to be tested.Accordingly, any other structure of comparable functionality maylikewise be employed. For example, other mechanical fasteners, orclamps, may alternatively be employed. In yet other implementations, thethermal testing assembly 200 is simply held in position by gravity,without the use of mechanical attachment structures or adhesives.

The cover plate 212 can be used to hold the TEC 204 in thermal contactwith the module 100. In this embodiment, the cover plate 212 can includeone or more grooves 234. The grooves 234 allow corresponding connectorpieces 225 on the clip 210 to recess within the cover plate 212. Thisallows the TEC 204 to rest generally flush against the cover plate 212,thus providing a large surface area for thermal contact. The cover plate212 exemplarily includes a slab or sheet of metal, or other materialhaving the desired thermal transmissive properties, to enable evenheating and/or cooling, as applicable, of the DUT when the TEC 204 isactivated. Accordingly, the cover plate 212 is configured and arrangedfor substantial thermal contact with TEC 204.

Among other things, the cover plate 212 facilitates measurement of thetemperature of the DUT to within, for example, about 0.5 degreesCelsius. To this end, a thermal sensor 214 is provided. This sensor 214connects the cover plate 212 with suitable temperature monitoringequipment (not shown). The information provided by this thermal sensor214 is exemplarily employed as part of a feedback system for controllingthe amount of current provided to the TEC 204. In this way, a preciseamount of current can be provided to the TEC 204 to maintain a desiredtemperature. Alternately, the thermal sensor 214 can be integrated intothe cover plate 212, the cover 202, or the TEC 204. In still otherconfigurations, a thermal or temperature sensor can be independentlymounted within the assembly 200.

The ability to control the TEC 204 in this way provides for a relativeimprovement in temperature control, as compared with typical testingmethods, such as those that rely on an oven or similar device toestablish and maintain a DUT at a desired temperature. Such control, inturn, enhances the quality, reliability and usefulness of the test dataobtained in connection with thermal testing of the module or othercomponent. Additionally, since no oven is used, it is much easier tocycle through numerous DUTs in a relatively short period of time. Sincethe TEC 204 is in thermal contact with the DUT, changing the temperatureof the DUT is done much faster than with prior systems.

In this embodiment, washers 216 and mechanical fasteners 218,exemplarily implemented as screws, rivets or bolts, are provided thatremovably secure the cover 202, the TEC 204, the clip 210, and the coverplate 212 to each other, as generally indicated in FIG. 2, as themechanical fastener 218 threadably engages with corresponding threadedholes 230 in the cover plate 212. It is understood that adhesives canalso be used in addition to, or in place of, mechanical fasteners.Moreover, such mechanical fasteners may comprise metallic materials, ornon-metallic materials such as nylon, or plastics. Using thermallyconductive materials, such as metallic materials and certain ceramicmaterial, reduces the overall thermal separation needed between thecover 202 and the cover plate 212. Additionally, elastomeric fasteners,such as a rubber band designed to withstand the temperatures within thedesired test range, can also be used to hold the components in a fixedrelationship with respect to each other.

With continuing reference to FIG. 2A, at least some implementations ofthe thermal testing assembly 200 further include a heat sink 220, thatcan be made from a thermally conductive material, such as metal forexample, that is positioned on top of the cover 202 to enable heatdissipation. In alternate embodiments, the heat sink 220 is attached tothe cover 202 using chemical or mechanical fasteners. In yet otherembodiments, one example of which is shown in FIG. 2B, the heat sink 220and cover 202 can be formed as an integrated unit. Various types ofmetals, including, but not limited to, aluminum and aluminum alloys, maybe employed in the construction of the heat sink 220, but any othersuitable metals or other thermally conductive materials mayalternatively be employed. Aspects of the heat sink 220 such as, but notlimited to, heat transfer area, size, geometry, positioning, andorientation may be varied as necessary to suit the requirements of aparticular application. Accordingly, the scope of the invention shouldnot be construed to be limited to the exemplary heat sinkimplementations disclosed herein.

One alternate exemplary embodiment of a thermal testing assembly isshown in FIG. 2B, and designated generally with reference numeral 250.Thermal testing assembly 250 includes a cover 252 that, among otherthings, isolates the assembly from the ambient air temperature. Thethermal testing assembly 250 further includes a thermoelectric cooler(TEC) 254 that is located substantially within, and which is in thermalcontact with the cover 252. Alternately, the TEC 254 can be attached tothe cover 252. In the illustrated configuration, there can be a clip 260located below and attached to the TEC 254. The clip 260 can be designedto hold the thermal assembly 250 onto a cage assembly 288 housing thedevice under test (DUT). The thermal testing assembly 250 furtherincludes a cover plate 262 that is secured against the optoelectronicdevice under test using the clip 260 and is simultaneously held inthermal contact with the TEC 254.

In this exemplary embodiment, the cover 252 can be designed as a unitarypiece that includes a heat sink, including a plurality of heatdissipating fins 270. The cover 252 can be substantially comprised of athermally conductive material, such as metal, to enable heat transfer.Examples of such metals can include, but are not limited to, aluminum,aluminum alloys, copper, and/or copper alloys. The cover 252 exemplarilyincludes shield portions 253 that serve to at least partially isolatethe TEC 254 and cage assembly 288 from air currents or other influencesthat may compromise the performance of the thermal testing assembly 250.The geometry, positioning and orientation of the shield portions 253 areexemplary only. The shield portions 253 may, more generally, beimplemented, arranged, and/or oriented in any fashion that a particularsituation or application may require.

As noted earlier herein, the thermal testing assembly 250 includes theTEC 254 located substantially within, and attached to the cover 252.Electrical supply wires 256 and 258 can connect to the TEC 254 forconnection with an electrical power source (not shown) for operation ofthe TEC 254. The TEC 254 serves to establish and maintain the DUT at adesired temperature. Examples of such DUTs can include, by way ofexample and not limitation, the module 100 (see FIG. 1), or any otherelectronic device, optical device, or other configurations ofoptoelectrical or electrical devices. Module 100 can be, by way ofexample and not limitation, an XFP module, an SFF module, an SFP module,an SFX module, an AT module, a GBIC module and/or other modules known tothose of skill in the art.

In the embodiment illustrated in FIG. 2B, the cage 288 is designed toreceive an XFP module. In some implementations, the TEC 254 is alsoemployed to change the temperature of a given DUT. Depending on themanner in which current is supplied to the TEC 254, the TEC 254 may beemployed to either heat or cool the DUT, or to maintain the DUT at adesired operational temperature, as discussed in more detail below.

The clip 260 enables the thermal testing assembly 250 to be removablyattached to the cage assembly 288. For instance, the clip 260 caninclude grooves 272 on arm portions 274 that receive and releasably holdthe cage assembly 288 that houses the DUT. Examples of such DUTs caninclude the module 100 (see FIG. 1), or any other electronic, optical orother device upon which thermal testing is to be conducted.

The cover plate 262 can be used to hold the TEC 254 in thermal contactwith the module 100 when the module 100 is inserted into the cageassembly 288. In this embodiment, the cover plate 262 can include one ormore grooves 284. The grooves 284 allow corresponding connector pieces275 on the clip 260 to recess within the cover plate 262. This allowsthe TEC 254 to rest generally flush against the cover plate 262, thusproviding a large surface area for thermal contact. The cover plate 262exemplarily includes a slab or sheet of metal, or other material havingthe desired thermal transmissive properties, to enable even heatingand/or cooling, as applicable, of the DUT when the TEC 254 is activated.Accordingly, the cover plate 262 can be configured and arranged forsubstantial thermal contact with TEC 254.

Among other things, the cover plate 262 facilitates measurement of thetemperature of the DUT to within, for example, about 0.5 degreesCelsius. To this end, a thermal sensor 264 can be provided. This sensor264 connects the cover plate 262 with suitable temperature monitoringequipment (not shown). The information provided by this thermal sensor264 can be exemplarily employed as part of a feedback system forcontrolling the amount of current provided to the TEC 254. In this way,a precise amount of current can be provided to the TEC 254 to maintain adesired temperature. Alternately, the thermal sensor 264 can beintegrated into the cover plate 262, the cover 252, or the TEC 254. Instill other configurations, a thermal or temperature sensor can beindependently mounted within the assembly 250.

As with the system shown in FIG. 2A, the ability to control the TEC 254in this way provides for a relative improvement in temperature control,as compared with typical testing methods, such as those that rely on anoven or similar device to establish and maintain a DUT at a desiredtemperature. Such control, in turn, enhances the quality, reliabilityand usefulness of the test data obtained in connection with thermaltesting of the module or other component. Additionally, since no oven isused, it is much easier to cycle through numerous DUTs in a relativelyshort period of time. Since the TEC 254 is in thermal contact with theDUT, changing the temperature of the DUT can be achieved much fasterthan with prior systems.

In this embodiment, mechanical fasteners 268, exemplarily implemented asscrews, rivets or bolts, are provided that removably secure the cover252, the TEC 254, the clip 260, and the cover plate 262 to each other,as generally indicated in FIG. 2B, as the mechanical fastener 268threadably engages with corresponding threaded holes 280 and 282 in thecover plate 262. It is understood that adhesives can also be used inaddition to, or in place of, mechanical fasteners. Moreover, suchmechanical fasteners may comprise metallic materials, or non-metallicmaterials such as nylon, or plastics. Using thermally conductivematerials, such as metallic materials and certain ceramic material,reduces the overall thermal separation needed between the cover 252 andthe cover plate 262. Additionally, elastomeric fasteners, such as arubber band designed to withstand the temperatures within the desiredtest range, can also be used to hold the components in a fixedrelationship with respect to each other.

The cage 288 can be mounted to a substrate 299. In some embodiments,substrate 299 can be a PCB that includes other circuitry for use in theoperation of the test equipment. The cage 288 can include an opening 290designed to accommodate a particular type of electronic oroptoelectronic module. Examples of such modules can include an XFPmodule, an SFF module, an SFP module, an SFX module, an AT module, aGBIC module and/or other modules known to those of skill in the art. Thecage 288 can also include one or more windows 292 that allow variouselectrical or other connections to exit an interior 294 of the cage 288.In one assembled configuration, the cover plate 262 can be recessedwithin the interior 294 of the cage 288, such that when a DUT isinserted into the opening 290, thermal contact is established andmaintained between the DUT and the TEC 254 through the cover plate 262.

Directing attention now to FIGS. 3 and 4, details are providedconcerning aspects of a module test system 300 such as may be employedin connection with implementations of thermal testing assemblies 200 and250 (see, e.g., FIGS. 2A and 2B). In the illustrated implementation, themodule test system 300 includes a PCB 302 mounted on a base member 304.Attached to the base member 304 is a cage 306 that is sized andconfigured to securely and removably receive a device, such as anoptoelectronic module. A connector 308 located proximate the cage 306enables the DUT (not shown) to electrically and mechanically interfacewith circuitry disposed on the PCB 302. A connection 310, such as anoptical fiber for example, enables output from the DUT to be directed toa digital communications analyzer (DCA) 312, or other devices ofcomparable functionality.

As discussed in further detail below, control of the DUT test system 300and the thermal test system 200 is generally implemented in connectionwith a host computer 314 configured to communicate with the DUT by wayof a bus 316 and the connector 308, and also to communicate with the DCA312 (or other devices) by way of bi-directional bus 318. Among otherthings, the host computer 314 causes transmission of test signals, whichmay also be referred to herein as “test data patterns,” to theoptoelectronic module, or other DUT, so that the response of the device,exemplified as an output signal, can be evaluated and correspondingadjustments implemented if necessary. As discussed in further detailelsewhere herein, the thermal testing assembly 200 and the host computer314 enable testing of various components of the module 100, such as, butnot limited to, the ROSA and/or TOSA, over a range of thermalconditions. In alternate embodiments, no host computer is required, andtesting can be accomplished manually using, for example, the analyzer312, or any other equipment capable of generating the electrical/opticalsignal initially sent to the transceiver.

In one testing evolution, a test data pattern is transmitted to an OSAwhich, in the case of a TOSA for example, converts the test data patterninto an optical signal. The output optical signal is then analyzed forconformance with various standards in order to determine the effect(s)of the imposed thermal conditions on the performance of the device. Thiswill be discussed in more detail below with reference to FIG. 6.

In the illustrated implementation, host computer 314 includes a userinterface 320 which generally enables a user to input programming and/orother instructions, and also allows a user to access informationconcerning testing evolutions, setups and processes. The user interface320 may be implemented, for example, as a graphical user interface (GUI)or other suitable user interface. The host computer 314 further includesone or more interfaces 322 for connection to the PCB 302, and also caninclude a central processing unit (CPU) 324 and a memory 326. In thisexemplary implementation, the memory 326 includes high speed randomaccess memory (RAM) as well as nonvolatile mass storage, such as one ormore magnetic disk storage devices. In other implementations, the memory326 additionally, or alternatively, includes mass storage that isremotely located from central processing unit(s) 324. The memory 326exemplarily includes a suitable operating system 328, a test controlprogram 330 and a test result database 332, as well as other systems andprograms.

The host computer 314 can be a special purpose or general purposecomputer that includes various computer hardware, as discussed ingreater detail below. Embodiments within the scope of the presentinvention can also include computer-readable media for carrying orhaving computer-executable instructions or electronic content structuresstored thereon. Such computer-readable media can be any available mediawhich can be accessed by a general purpose or special purpose computer.By way of example, and not limitation, such computer-readable media cancomprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to carry or store desired program code means inthe form of computer-executable instructions or electronic contentstructures and which can be accessed by a general purpose or specialpurpose computer.

When information is transferred or provided over a network or anothercommunications connection (either hardwired, wireless, or a combinationof hardwired or wireless) to a computer, the computer properly views theconnection as a computer-readable medium. Thus, any such a connection isproperly termed a computer-readable medium. Combinations of the aboveshould also be included within the scope of computer-readable media.Computer-executable instructions comprise, for example, instructions andcontent which cause a general purpose computer, special purposecomputer, or special purpose processing device to perform a certainfunction or group of functions.

Although not required, aspects of the invention are described herein inthe general context of computer-executable instructions, such as programmodules, being executed by computers in network environments. Generally,program modules include routines, programs, objects, components, andcontent structures that perform particular tasks or implement particularabstract content types. Computer-executable instructions, associatedcontent structures, and program modules represent examples of theprogram code means for executing steps of the methods disclosed herein.The particular sequence of such executable instructions or associatedcontent structures represents examples of corresponding acts forimplementing the functions described in such steps.

Of course, exemplary embodiments of the invention may be practiced innetwork computing environments with many types of computer systemconfigurations, including personal computers, hand-held devices,multi-processor systems, microprocessor-based or programmable consumerelectronics, network PCs, minicomputers, mainframe computers, and thelike. The invention may also be practiced in distributed computingenvironments where tasks are performed by local and remote processingdevices that are linked (either by hardwired links, wireless links, orby a combination of hardwired or wireless links) through acommunications network. In a distributed computing environment forexample, program modules may be located in both local and remote memorystorage devices. Alternately, exemplary embodiments of the presentinvention can be practiced in a stand alone system configuration.

Returning to FIG. 3, the operating system 328 generally includesinstructions for performing functions such as, but not limited to,communicating, processing data, accessing data, analyzing data, storingdata, and searching data. The test control program 330 generallydefines, and causes the execution of, various thermal tests andexemplarily includes a DCA control module 334, a bit error rate tester(“BERT”) control module 336, and a test data evaluation module 338. Inthis exemplary configuration, the host computer 314 has the ability togenerate and/or receive a test electrical signal.

Directing particular attention now to FIG. 4, and with continuingattention to FIG. 3, an arrangement of the module test system 300 showsthe exemplary module 100 operably received in the cage 306 (shownpartially in phantom) and the thermal testing assembly 200 positionedover the cage 306. Note that in some alternative implementations, nocage 306 is provided. However, the cage 306 is desirable in at leastsome cases because the cage 306 facilitates a secure connection betweenthe electrical connector 112 (see FIG. 1) of the module 100 and theconnector 308. The cage 306 also facilitates a secure connection betweenthe thermal test assembly 200 and the module 100. The clip 210 (FIG. 2)can be designed to fasten onto the cage 306 creating optimal thermalconnection between the entire assembly 200 and the module 100. In somealternative implementations, the thermal testing assembly 200 is placeddirectly on the device to be tested.

As noted earlier herein, the module test system 300 can include anoptical test pattern generator. Analysis of the test data pattern forcompliance with operating requirements may be performed manually byviewing a scope, such as the DCA 312, that graphically displays theoutput signal of the DUT. Alternately, this analysis can be performedautomatically by the host computer 314, or other devices suitable tothat purpose. This, and similar analyses, enable the user to identifythe effect of the thermal test conditions on the data stream output bythe test device. Aspects of the testing evolution can then be modified,if desired, such as by communication of instructions to the hostcomputer 314 by the test operator. Specific examples of methods andprocedures for use of the module test system 300 with the thermaltesting assembly 200 are discussed below in connection with FIG. 6.

Generally, the host computer 314 controls the test data conditions, aswell as the functioning of the test pattern generator and the DCA 312.With reference to the illustrated implementation of FIG. 4, anelectrical test signal is fed from the host computer 314 to, forexample, a TOSA port of the module 100, by way of the PCB 302, the bus316, and the connector 308. The TOSA converts the electrical test signalto an output optical signal which is then transmitted from the module100 through an optical fiber 310 and is received by the DCA 312,electrically coupled to the host computer 314 by way of thebi-directional bus 318. The DCA 312 analyzes the test signal forcompliance with operating requirements, and transmits the results of itsanalysis to the host computer 314.

In some implementations, the host computer 314 can adjust one or moreaspects of the test, based upon results of the analyses performed by theDCA 312 or by the host computer 314. For example, the host computer 314can adjust the electronics on the PCB 302 of the module 100, thuschanging the performance of the TOSA and/or ROSA until they functionproperly. The host computer 314 also performs additional analyses insome implementations. By way of example, test data can be gathered atanother operating temperature, or over a range of operatingtemperatures, and sent to the host computer 314 for analysis andevaluation. The test data results can then be stored in the hostcomputer 314 for later use.

Details concerning the conduct of one testing method are provided withreference to FIG. 6. In general, test result data is received from themodule 100, by way of the DCA 312, and stored in the test resultdatabase 332 of FIG. 3. With continued reference to FIG. 3, the testcontrol program 330 and the DCA control module 334 include computerprograms and/or instructions for controlling the operation of and forreceiving test result data from, the DCA 312. The test evaluation module338 includes instructions for evaluating the test result data todetermine whether the optical component is functioning properly underthe imposed thermal conditions. Note that in one alternativeimplementation of the module test system 300, discussed below inconnection with FIG. 5, a BERT is used to implement at least some of thefunctions implemented in connection with the DCA 312 illustrated inFIGS. 3 and 4

With attention now to FIG. 5, details are provided concerning analternate implementation, designated as reference numeral 350, of themodule test system shown in FIG. 3. As the implementation of the moduletest system illustrated in FIG. 5 is similar in many regards to thatillustrated in FIG. 3, the following discussion of FIG. 5 will focusprimarily on selected aspects of the embodiment illustrated there.

In contrast with the implementation of the module test system shown inFIG. 3, the implementation illustrated in FIG. 5 employs a BERT 315rather than the DCA 312. In this exemplary embodiment, the host computer314 controls the operation of the BERT 315 by way of the BERT controlmodule 336 (see FIG. 3) and a bi-directional bus 354.

Generally, the BERT 315 generates and transmits test data patterns tothe DUT in response to instructions received from the host computer 314.As noted above, the DUT generates and transmits a corresponding outputsignal. In the illustrated embodiment, the signal generated andtransmitted by the DUT is directed to the BERT 315, which then analyzesthe output signal of the device to determine a bit error rate (BER)associated with the DUT undergoing the testing. Alternately, the signalgenerated by the DUT can be sent directly to the host computer 314,using an appropriate hardware interface. The host computer 314 thenperforms the analysis of the signal.

The measured BER can then be used to evaluate the effect of variousthermal conditions on the performance of the DUT. It should be notedhowever that the scope of the invention is not limited for use inconnection with the BER performance parameter. More generally,embodiments of the invention may be employed in connection with anyother performance parameter(s) that provide(s) a measure of performanceor response of the DUT as a function, whether direct or indirect, of thethermal condition(s) to which the device is subjected. Such otherparameters can include, by way of example and not limitation, analysisby the DCA of the electrical signal outputted from the ROSA, use of aJitter tester to ensure proper behavior, and/or use of a networkanalyzer to ensure proper behavior within a system

Use of the module test system 350 to test a ROSA, for example, issimilar to the testing of a TOSA as discussed above with reference toFIG. 4. An optical test pattern generator, such as the BERT 315, havingan optical transmitter at its output port, is configured to transmittest signal transmissions to the module 100 via a fiber optic connection352. In some implementations, the fiber optic connection 352 takes theform of two fiber optic lines, one for transmission and one forreception. The BERT 315 is connected via the bus 316 to the PCB 302. TheBERT 315 is also connected to the host computer 314 for transmitting andreceiving test data and commands via the bi-directional bus 354.

The host computer 314 controls the test data conditions as well as thefunctioning of the optical test pattern generator. An optical testpattern is fed from the BERT 315 to, for example, the ROSA of the module100, via the fiber optic connection 352. The ROSA then converts theinput test pattern to an electrical output signal which is thentransmitted to the BERT 315 via the PCB 302 and the bus 316. The BERT315 passes this signal on to the host computer 314, by way of the busand the host computer 314 then analyzes the received signal inconjunction with data received from the BERT 315 for compliance withpre-programmed operating requirements. Alternately, additional moduleswithin the BERT 315 can conduct the analysis and send the results to thehost computer 314.

Based upon the analysis of the test results, the host computer 314 thentransmits commands to the BERT 315 for further adjustment of the controlparameters, such as repeating the testing over a range of moduletemperatures, if necessary. The test data results can then be stored inthe host computer 314 for later use. Alternately, the test data resultscan be transmitted to a remote location via a network or otherconnection with the host computer 314. In addition, the host computer314 may send commands to the PCB 302 to adjust the performance of theROSA portion of the module 100 or to adjust other operating parametersof the PCB 302 or the TEC 204 (see FIG. 2), and/or other componentsassociated with the module test system and/or the thermal testingassembly. It should be noted that the scope of the present invention isnot limited to the exemplary layout of circuits and testing apparatusesdisclosed herein.

With attention now to FIG. 6, details are provided concerning aspects ofone embodiment of a thermal testing method, denoted generally asreference numeral 600. In the illustrated implementation, the process600 commences by preheating the optoelectronic module to be tested to apredetermined temperature, as represented by block 602. This preheatprocess reduces the time required to conduct the test since preheatingcan often be implemented relatively more quickly with systems anddevices other than the thermal testing assembly. In otherimplementations however, no preheating is performed.

Following preheating, the module 100 can be positioned on the test boardand can be electrically and optically connected to the elements of themodule test system, as disclosed elsewhere herein and represented byblock 604. In one embodiment, module 100 is positioned within the cage306 (FIGS. 4 and 5). Upon mounting the module 100, the sensor measuresthe temperature of the module casing, and sends this data to theoperator, and/or the host controller and host computer, to determine ifthe module 100 has reached the desired temperature, as represented bydecision block 606. If the module is at the desired test temperature, asrepresented by decision block 606 being in the affirmative, the process600 advances to transmit a test data stream or data pattern to themodule 100, as represented by block 610. If, on the other hand, themodule is not at the desired test temperature, the process 600 advancesto stage 608 where the TEC of assembly 200 is energized until the moduleattains the desired test temperature.

In either case, the module ultimately receives the test data stream andgenerates and transmits a corresponding output data stream to a devicesuch as the host computer, DCA or BERT. At stage 612 of the process 600,this output data stream is evaluated. Among other things, thisevaluation process ensures that the module is operating withinacceptable operating parameters. These operating parameters can be, byway of example and not limitation, those specified by the current XFPMulti-Source Agreement (MSA) Specification, SONET OC-192 SR-1 and SDHSTM I-64.1 specifications, as well as the 10-Gigabit Ethernet, IEEE802.3ae, 10 GBASE-LR/LW, and 10 G Fibre Channel specifications. Anyother predefined specification can also be used, whether or not suchspecification includes predefined operating parameters defined by thestandards outlined above.

The process then advances to decision point 614, where it is determinedwhether or not the module is operating within acceptable parameters. Ifthe module is not operating within acceptable parameters, then one ormore of the module operating parameters can be changed, as shown instage 616. The process then returns to stage 610, and a new data streamis transmitted. After evaluation of the output data stream has beencompleted, and the module is operating within acceptable specifications,the process 600 advances to decision point 618 where a determination ismade as to whether or not the entire range of temperatures has beentested. If not, the process 600 returns to stage 608. If the entirerange of temperatures has been tested, the process advances to stage 620where a determination is made as to whether there are additional modulesto be tested. If further modules are to be tested, the process 600returns to stage 604. On the other hand, if there are no further modulesto be tested, testing is then complete and the process 600 terminates atstage 622.

Exemplary embodiments of the present invention allow for testing ofoptoelectronic devices over a wide temperature range. In one exemplaryimplementation, the module test system tests modules or other componentsover a range of about 15° C. to about 90° C. and/or at discretetemperatures within that range. In one exemplary embodiment,optoelectronic transceiver modules are tested over a range of about 25°C. to about 71° C. The foregoing are exemplary test conditions onlyhowever and, more generally, any of a variety of other thermal testconditions may be defined and employed. For example, a range of about−40° C. to about 100° C. can be used. Further, aspects of thermaltesting such as, but not limited to, range of temperatures, duration ofthermal test, thermal cycling, and thermal gradients may be varied asnecessary to suit the requirements of a particular application ormodule.

The thermal testing assemblies of the present invention enable full datarate testing of optoelectronic devices, such as transceivers, at datarates ranging from, for example, about 1 Gb/s to about 11 Gb/s. Suchtesting helps to ensure that transceivers that are shipped to customerswill perform as specified, thus greatly reducing module failures andincreasing customer satisfaction.

The test devices, systems and methods outlined herein provide manyadvantages over prior systems and methods. Since the entire testapparatus is not heated in an oven, failure of the test systemelectrical circuits is no longer a problem. The accuracy of the testtemperature is increased, since the module test temperature can now bemeasured to within, for example 0.5° C. In alternate embodiments,depending on the equipment used, the module test temperature can bemeasured and/or adjusted to within 0.05° C. Since only the module isheated, changing the test temperature of the module also occurs morequickly and the corresponding temperatures are more accurate andconstant. Additionally, it is now much easier and faster to testadditional modules over the desired temperature range.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

1. A method for thermal testing of an optoelectronic module, the methodcomprising the steps of: placing the module in a thermal testingassembly and making electrical and/or optical connections to a testingdevice, said thermal testing assembly comprising: a frame; athermoelectric cooler in thermal contact with said frame; a cover platein thermal contact with the thermoelectric cooler; and means forremovably attaching the thermal testing assembly to the module; bringingthe module to a desired testing temperature; transmitting a data streamfrom said testing device through the module; evaluating said data streamagainst a predefined standard; and based on the evaluation of said datastream, adjusting at least one operating parameter of the module untilthe module meets said predefined standard.
 2. The method of claim 1,further comprising an initial step of preheating the module to thedesired testing temperature.
 3. The method of claim 1, furthercomprising a step for changing said test temperature and repeating saidtransmitting, evaluating and adjusting steps.
 4. The method of claim 1,wherein said desired testing temperature is between −40° C. and 100° C.5. The method of claim 1, wherein a predetermined specificationassociated with the optoelectronic module forms a basis for evaluatingthe data stream.
 6. The module test system of claim 5, wherein saidpredetermined standard comprises one of the following specifications:XFP MSA Specification; SONET OC-192 SR-1; SDH STM I-64.1; 10-GigabitEthernet; IEEE 802.3ae; 10 GBASE-LR/LW; and, 10 G Fibre Channel.
 7. Themethod of claim 1, wherein a bit error rate associated with theoptoelectronic module forms a basis for evaluating the data stream.